使用隱形偏光標記及可見光通訊之室內擴增實境導航系統

Abstract

本論文實作使用偏光標記及可見光通訊結合之室內擴增實境導航系 統。偏光片為一高分子多層複合材料，其物理機制為：將非偏振的入 射光加以過濾，只有與透射軸平行的光才可進入，另一部份則是藉由 吸收、反射和散射等作用使其遮蔽，由於偏光片有著製造工藝簡單、 價格便宜的優點，使其易於大量生產。可見光通訊則是一種新型的資 料傳輸技術，由於LED 具壽命長、低功耗、高效率之優點，使得其逐 漸取代傳統日光燈照明。基於其兼具照明及通訊之特性，其在室內定 位上具有極大的應用潛力。 我們利用一般相機作為接收端，以及市售的LED 燈具當作傳輸端， 因此不需要太多額外的花費即可使用此系統。我們的發想是：利用拍 攝貼在天花板的LED 燈具上的偏光標記，即可得知使用者及其相對的 角度，在透過LED 燈具傳輸絕對位置，便可達到室內定位及導航的功 能，此技術可適用於所有有裝設LED 照明系統的室內場所。 我們希望可以利用單顆燈及單張相片就可達到定向效果，但由於拍 攝偏光標記的畫素、距離不盡相同，每次拍攝出來的不一定為最理想 情況，因此我們設計出兩種計算相對角度的方法。我們在不同距離的 手持高度下進行實驗，測量其角度誤差，並且提出在現實應用情境下， 使用多張影像進行角度校正之方法。經實驗證實此兩種方法適用於不 同距離及解析度的情況，其誤差精準度在距離250cm 內可到達10 度內 之誤差。

This thesis presents an augmented reality indoor navigation system with invisible polarizer marker and visible light communications (VLC). Polarizer is a polymer multi-layer composite materials. It has a physical property that human eyes cannot distinguished the intensity of polarized light passed though by only one polarizer. But the intensity can be discriminated and controlled by adding another polarization filter with a different polarization direction. VLC is a new wireless communication technology. LED has gradually replaced the traditional fluorescent lighting because its advantages of long life, low power consumption, and high efficiency. Due to its properties of high energy efficiency and fast response time, LED has a great potential for indoor positioning. In our proposed system, we use commodity camera as the receiver and modify off-the-shelf LED light to become the transmitter, and thus it requires minimal additional cost. The main idea is that when the camera captures images with the polarizer marker on the ceiling light fixture, the orientation angle between the camera and polarizer marker can be estimated. Utilizing VLC, at the time the LED also transmits its absolute location to the camera. The device can then use these two pieces of information to estimate its own absolute location when more than one LED light is captured in the image. This solution is highly attractive for any indoor environment with LED lighting, due to our design goal is to be able to estimate the orientation of the device with a single image capture. In this thesis, we present two methods to estimate the orientation angle between marker and the camera using a single image: the ratios between the pixel intensity of different marker areas, and the orientation of the marker in the image. We also propose a method to mitigate the error with multiple images. Our system is evaluated with different image resolutions and distances between the light and the camera. Results show that the mean angle error is always less than 10◦ for a distance up to 2.5 meters.